1. Field of the Invention
One embodiment of the present invention relates to an object, a method, or a manufacturing method. One embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. One embodiment of the present invention particularly relates to a semiconductor device and a driving method thereof. Another embodiment of the present invention relates to a display device including a semiconductor device and a driving method thereof.
In this specification and the like, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics. Thus, a semiconductor element such as a transistor or a diode and a semiconductor circuit are semiconductor devices. A display device, a light-emitting device, a lighting device, an electro-optical device, an imaging device, an electronic device, and the like may include a semiconductor element or a semiconductor circuit. Therefore, a display device, a light-emitting device, a lighting device, an electro-optical device, an imaging device, an electronic device, and the like include a semiconductor device in some cases.
2. Description of the Related Art
An active-matrix display device where a transistor for driving a display element is provided in each pixel is known. For example, an active-matrix liquid crystal display device that includes a liquid crystal element as a display element, an active-matrix light-emitting display device that includes a light-emitting element, such as an organic EL element, as a display element, and the like are known. These active-matrix display devices are easier to increase in display size or definition than simple-matrix display devices, and have an advantage in reduced power consumption and the like.
In light-emitting display devices, if the threshold voltage or mobility varies among transistors that control the values of currents supplied to light-emitting elements in accordance with image signals (driver transistors), the luminance also varies among the light-emitting elements. To prevent the variation in the luminance of the light-emitting elements due to the variation in threshold voltage or mobility, a display device in which the threshold voltage or mobility of transistors is corrected inside pixels and a display device in which a variation in the threshold voltage or mobility of transistors is obtained and correction is made outside pixels are disclosed in Patent Document 1.